High resistivity silicon-on-insulator substrate having enhanced charge trapping efficiency

ABSTRACT

A multilayer semiconductor on insulator structure is provided in which the handle substrate and an epitaxial layer in interfacial contact with the handle substrate comprise electrically active dopants of opposite type. The epitaxial layer is depleted by the handle substrate free carriers, thereby resulting in a high apparent resistivity, which improves the function of the structure in RF devices.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. provisional application Ser.No. 62/412,937, which was filed Oct. 26, 2016, the disclosure of whichis hereby incorporated by reference as if set forth in its entirety.

FIELD OF THE INVENTION

Semiconductor wafers are generally prepared from a single crystal ingot(e.g., a silicon ingot) which is trimmed and ground to have one or moreflats or notches for proper orientation of the wafer in subsequentprocedures. The ingot is then sliced into individual wafers. Whilereference will be made herein to semiconductor wafers constructed fromsilicon, other materials may be used to prepare semiconductor wafers,such as germanium, silicon carbide, silicon germanium, gallium arsenide,and other alloys of Group III and Group V elements, such as galliumnitride or indium phosphide, or alloys of Group II and Group VIelements, such as cadmium sulfide or zinc oxide.

Semiconductor wafers (e.g., silicon wafers) may be utilized in thepreparation of composite layer structures. A composite layer structure(e.g., a semiconductor-on-insulator, and more specifically, asilicon-on-insulator (SOI) structure) generally comprises a handle waferor layer, a device layer, and an insulating (i.e., dielectric) film(typically an oxide layer) between the handle layer and the devicelayer. Generally, the device layer is between 0.01 and 20 micrometersthick, such as between 0.05 and 20 micrometers thick. Thick film devicelayers may have a device layer thickness between about 1.5 micrometersand about 20 micrometers. Thin film device layers may have a thicknessbetween about 0.01 micrometer and about 0.20 micrometer. In general,composite layer structures, such as silicon-on-insulator (SOI),silicon-on-sapphire (SOS), and silicon-on-quartz, are produced byplacing two wafers in intimate contact, thereby initiating bonding byvan der Waal's forces, followed by a thermal treatment to strengthen thebond. The anneal may convert the terminal silanol groups to siloxanebonds between the two interfaces, thereby strengthening the bond.

After thermal anneal, the bonded structure undergoes further processingto remove a substantial portion of the donor wafer to achieve layertransfer. For example, wafer thinning techniques, e.g., etching orgrinding, may be used, often referred to as back etch SOI (i.e., BESOI),wherein a silicon wafer is bound to the handle wafer and then slowlyetched away until only a thin layer of silicon on the handle waferremains. See, e.g., U.S. Pat. No. 5,189,500, the disclosure of which isincorporated herein by reference as if set forth in its entirety. Thismethod is time-consuming and costly, wastes one of the substrates andgenerally does not have suitable thickness uniformity for layers thinnerthan a few microns.

Another common method of achieving layer transfer utilizes a hydrogenimplant followed by thermally induced layer splitting. Particles (atomsor ionized atoms, e.g., hydrogen atoms or a combination of hydrogen andhelium atoms) are implanted at a specified depth beneath the frontsurface of the donor wafer. The implanted particles form a cleave planein the donor wafer at the specified depth at which they were implanted.The surface of the donor wafer is cleaned to remove organic compounds orother contaminants, such as boron compounds, deposited on the waferduring the implantation process.

The front surface of the donor wafer is then bonded to a handle wafer toform a bonded wafer through a hydrophilic bonding process. Prior tobonding, the donor wafer and/or handle wafer are activated by exposingthe surfaces of the wafers to plasma containing, for example, oxygen ornitrogen. Exposure to the plasma modifies the structure of the surfacesin a process often referred to as surface activation, which activationprocess renders the surfaces of one or both of the donor water andhandle wafer hydrophilic. The surfaces of the wafers can be additionallychemically activated by a wet treatment, such as an SC1 clean orhydrofluoric acid. The wet treatment and the plasma activation may occurin either order, or the wafers may be subjected to only one treatment.The wafers are then pressed together, and a bond is formed therebetween. This bond is relatively weak, due to van der Waal's forces, andmust be strengthened before further processing can occur.

In some processes, the hydrophilic bond between the donor wafer andhandle wafer (i.e., a bonded wafer) is strengthened by heating orannealing the bonded wafer pair. In some processes, wafer bonding mayoccur at low temperatures, such as between approximately 300° C. and500° C. In some processes, wafer bonding may occur at high temperatures,such as between approximately 800° C. and 1100° C. The elevatedtemperatures cause the formation of covalent bonds between the adjoiningsurfaces of the donor wafer and the handle wafer, thus solidifying thebond between the donor wafer and the handle wafer. Concurrently with theheating or annealing of the bonded wafer, the particles earlierimplanted in the donor wafer weaken the cleave plane.

A portion of the donor wafer is then separated (i.e., cleaved) along thecleave plane from the bonded wafer to form the SOI wafer. Cleaving maybe carried out by placing the bonded wafer in a fixture in whichmechanical force is applied perpendicular to the opposing sides of thebonded wafer in order to pull a portion of the donor wafer apart fromthe bonded wafer. According to some methods, suction cups are utilizedto apply the mechanical force. The separation of the portion of thedonor wafer is initiated by applying a mechanical wedge at the edge ofthe bonded wafer at the cleave plane in order to initiate propagation ofa crack along the cleave plane. The mechanical force applied by thesuction cups then pulls the portion of the donor wafer from the bondedwafer, thus forming an SOI wafer.

According to other methods, the bonded pair may instead be subjected toan elevated temperature over a period of time to separate the portion ofthe donor wafer from the bonded wafer. Exposure to the elevatedtemperature causes initiation and propagation of cracks along the cleaveplane, thus separating a portion of the donor wafer. The crack forms dueto the formation of voids from the implanted ions, which grow by Ostwaldripening. The voids are filled with hydrogen and helium. The voidsbecome platelets. The pressurized gases in the platelets propagatemicro-cavities and micro-cracks, which weaken the silicon on the implantplane. If the anneal is stopped at the proper time, the weakened bondedwafer may be cleaved by a mechanical process. However, if the thermaltreatment is continued for a longer duration and/or at a highertemperature, the micro-crack propagation reaches the level where allcracks merge along the cleave plane, thus separating a portion of thedonor wafer. This method allows for better uniformity of the transferredlayer and allows recycle of the donor wafer, but typically requiresheating the implanted and bonded pair to temperatures approaching 500°C.

The use of high resistivity semiconductor-on-insulator (e.g.,silicon-on-insulator) wafers for RF related devices such as antennaswitches offers benefits over traditional substrates in terms of costand integration. To reduce parasitic power loss and minimize harmonicdistortion inherent when using conductive substrates for high frequencyapplications it is necessary, but not sufficient, to use substratewafers with a high resistivity. Accordingly, the resistivity of thehandle wafer for an RF device is generally greater than about 500Ohm-cm. With reference now to FIG. 1, a silicon on insulator structure 2comprising a very high resistivity silicon wafer 4, a buried oxide (BOX)layer 6, and a silicon device layer 10. Such a substrate is prone toformation of high conductivity charge inversion or accumulation layers12 at the BOX/handle interface causing generation of free carriers(electrons or holes), which reduce the effective resistivity of thesubstrate and give rise to parasitic power losses and devicenonlinearity when the devices are operated at RF frequencies. Theseinversion/accumulation layers can be due to BOX fixed charge, oxidetrapped charge, interface trapped charge, and even DC bias applied tothe devices themselves.

A method is required therefore to trap the charge in any inducedinversion or accumulation layers so that the high resistivity of thesubstrate is maintained even in the very near surface region. It isknown that charge trapping layers (CTL) between the high resistivityhandle substrates and the buried oxide (BOX) may improve the performanceof RF devices fabricated using SOI wafers. A number of methods have beensuggested to form these high interface trap layers. For example, withreference now to FIG. 2, one method of creating asemiconductor-on-insulator structure 20 (e.g., a silicon-on-insulator,or SOI) with a CTL for RF device applications is based on depositing anundoped polycrystalline silicon film 28 on a silicon substrate havinghigh resistivity 22 and then forming a stack of oxide 24 and top siliconlayer 26 on it. A polycrystalline silicon layer 28 acts as a highdefectivity layer between the silicon substrate 22 and the buried oxidelayer 24. See FIG. 2, which depicts a polycrystalline silicon film foruse as a charge trapping layer 28 between a high resistivity substrate22 and the buried oxide layer 24 in a silicon-on-insulator structure 20.An alternative method is the implantation of heavy ions to create a nearsurface damage layer. Devices, such as radiofrequency devices, are builtin the top silicon layer 26.

It has been shown in academic studies that the polycrystalline siliconlayer in between of the oxide and substrate improves the deviceisolation, decreases transmission line losses and reduces harmonicdistortions. See, for example: H. S. Gamble, et al. “Low-loss CPW lineson surface stabilized high resistivity silicon,” Microwave Guided WaveLett., 9(10), pp. 395-397, 1999; D. Lederer, R. Lobet and J.-P. Raskin,“Enhanced high resistivity SOI wafers for RF applications,” IEEE Intl.SOI Conf, pp. 46-47, 2004; D. Lederer and J.-P. Raskin, “New substratepassivation method dedicated to high resistivity SOI wafer fabricationwith increased substrate resistivity,” IEEE Electron Device Letters,vol. 26, no. 11, pp. 805-807, 2005; D. Lederer, B. Aspar, C. Lagha{tildeover (e)} and J.-P. Raskin, “Performance of RF passive structures andSOI MOSFETs transferred on a passivated HR SOI substrate,” IEEEInternational SOI Conference, pp. 29-30, 2006; and Daniel C. Kerr et al.“Identification of RF harmonic distortion on Si substrates and itsreduction using a trap-rich layer”, Silicon Monolithic IntegratedCircuits in RF Systems, 2008. SiRF 2008 (IEEE Topical Meeting), pp.151-154, 2008.

SUMMARY OF THE INVENTION

The present invention is directed to a method of preparing a multilayersubstrate, the method comprising: epitaxially depositing an epitaxiallayer on the front surface of a single crystal semiconductor handlesubstrate, wherein the single crystal semiconductor handle substratecomprises two major, generally parallel surfaces, one of which is thefront surface of the single crystal semiconductor handle substrate andthe other of which is a back surface of the single crystal semiconductorhandle substrate, a circumferential edge joining the front surface andthe back surface of the single crystal semiconductor handle substrate, acentral plane between the front surface and the back surface of thesingle crystal semiconductor handle substrate, and a bulk region betweenthe front and back surfaces of the single crystal semiconductor handlesubstrate, wherein the single crystal semiconductor handle substrate hasa minimum bulk region resistivity of at least about 500 ohm-cm and theepitaxial layer has a resistivity between about 100 ohm-cm and about5000 ohm-cm; depositing a charge trapping layer on the epitaxial layer,the charge trapping layer comprising polycrystalline silicon having aresistivity of at least about 3000 ohm-cm; and bonding a dielectriclayer on a front surface of a single crystal semiconductor donorsubstrate to the charge trapping layer to thereby form a bondedstructure, wherein the single crystal semiconductor donor substratecomprises two major, generally parallel surfaces, one of which is thefront surface of the semiconductor donor substrate and the other ofwhich is a back surface of the semiconductor donor substrate, acircumferential edge joining the front and back surfaces of thesemiconductor donor substrate, and a central plane between the front andback surfaces of the semiconductor donor substrate.

The present invention is further directed to a method of preparing amultilayer substrate, the method comprising: epitaxially depositing anepitaxial layer on the front surface of a single crystal semiconductorhandle substrate, wherein the comprises single crystal semiconductorhandle substrate two major, generally parallel surfaces, one of which isthe front surface of the single crystal semiconductor handle substrateand the other of which is a back surface of the single crystalsemiconductor handle substrate, a circumferential edge joining the frontsurface and the back surface of the single crystal semiconductor handlesubstrate, a central plane between the front surface and the backsurface of the single crystal semiconductor handle substrate, and a bulkregion between the front and back surfaces of the single crystalsemiconductor handle substrate, wherein the single crystal semiconductorhandle substrate comprises an electrically active p-type dopant selectedfrom the group consisting of boron, aluminum, gallium, indium, and anycombination thereof and the epitaxial layer comprises an electricallyactive n-type dopant selected from the group consisting of arsenic,phosphorus, antimony, and any combination thereof, wherein theconcentration of the electrically active n-type dopant is less thanabout 1×10¹⁴ atoms/cm³; depositing a charge trapping layer on theepitaxial layer, the charge trapping layer comprising polycrystallinesilicon; and bonding a dielectric layer on a front surface of a singlecrystal semiconductor donor substrate to the charge trapping layer tothereby form a bonded structure, wherein the single crystalsemiconductor donor substrate comprises two major, generally parallelsurfaces, one of which is the front surface of the semiconductor donorsubstrate and the other of which is a back surface of the semiconductordonor substrate, a circumferential edge joining the front and backsurfaces of the semiconductor donor substrate, and a central planebetween the front and back surfaces of the semiconductor donorsubstrate.

The present invention is still further directed to a multilayerstructure comprising: a single crystal semiconductor handle substrate,wherein the single crystal semiconductor handle substrate comprises twomajor, generally parallel surfaces, one of which is a front surface ofthe single crystal semiconductor handle substrate and the other of whichis a back surface of the single crystal semiconductor handle substrate,a circumferential edge joining the front surface and the back surface ofthe single crystal semiconductor handle substrate, a central planebetween the front surface and the back surface of the single crystalsemiconductor handle substrate, and a bulk region between the front andback surfaces of the single crystal semiconductor handle substrate,wherein the single crystal semiconductor handle substrate comprises anelectrically active p-type dopant selected from the group consisting ofboron, aluminum, gallium, indium, and any combination thereof; anepitaxial layer in interfacial contact with the front surface of thesingle crystal semiconductor handle substrate, wherein the epitaxiallayer comprises an electrically active n-type dopant selected from thegroup consisting of arsenic, phosphorus, antimony, and any combinationthereof, wherein the concentration of the electrically active n-typedopant is less than about 1×10¹⁴ atoms/cm³; a charge trapping layer ininterfacial contact with the epitaxial layer, the charge trapping layercomprising polycrystalline silicon; a dielectric layer in interfacialcontact with the charge trapping layer; and a single crystalsemiconductor device layer in interfacial contact with the dielectriclayer.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a depiction of a silicon-on-insulator wafer comprising a highresistivity substrate and a buried oxide layer.

FIG. 2 is a depiction of a silicon-on-insulator wafer according to theprior art, the SOI wafer comprising a polysilicon charge trapping layerbetween a high resistivity substrate and a buried oxide layer.

FIGS. 3A through 3E depict a process flow according to some embodimentsof the present invention.

FIG. 4 is a graph demonstrating the resistivity of semiconductormaterial layered upon a substrate according to a structure of thepresent invention (engineered sample) and the resistivity ofsemiconductor material layered upon a substrate according to theconventional method (control sample).

FIG. 5 is a graph demonstrating the enhanced RF performance on theengineered substrates according to some embodiments of the presentinvention. The data are from coplanar wave guide device measurement.

DETAILED DESCRIPTION OF THE EMBODIMENT(S) OF THE INVENTION

According to the present invention, a method is provided for preparing asemiconductor-on-insulator composite structure (SOI, e.g., asilicon-on-insulator composite structure) comprising a charge trappinglayer (CTL). The present invention is further directed to asemiconductor-on-insulator composite structure (e.g., asilicon-on-insulator composite structure comprising a charge trappinglayer (CTL). This disclosure provides a method of engineering the singlecrystal semiconductor handle substrate to enhance electrical performanceof SOI structure used in radiofrequency devices.

In some embodiments, the present invention is directed to a method ofmanufacturing SOI wafers by engineering the interface between thepolycrystalline silicon charge trap layer (CTL) and the substrate (whichmay have a resistivity, in some embodiments, within the range of betweenabout 1,000 ohm-cm and about 6,000 Ohm-cm) to thereby significantlyimprove the performance of completed RF devices. In addition to thepolycrystalline silicon charge trapping layer, it has been demonstratedthat the substrate resistivity plays a role in suppressing the 2^(nd)and 3^(rd) harmonic distortion (HD2 and HD3). Increasing the substrateresistivity to >10,000 Ohm-cm (ultrahigh resistivity, UHR) minimizes thefree carriers so that the HD2/HD3 is more effectively suppressed. Itmay, however, be difficult to obtain and control such high resistivityby engineering the crystal pulling process as any contamination andprocess variation can lead to yield loss. Moreover, wafer thermalprocessing may lead to thermal donor generation from the oxygenincorporated during crystal growth process, which can change theresistivity or even flip the type of P-type substrates. Other processingissues caused by the UHR substrates may include wafer handling byelectric chuck, metrology challenge requires a certain conduction, likecapacitance gauge, SRP, etc. Furthermore, contaminants such as boron andaluminum which are trapped at the bond interface can readily diffusethrough the polycrystalline silicon and reduce the resistivity of thepolycrystalline silicon layer or induce recrystallization of thepolycrystalline silicon layer either of which again reduces theeffectiveness of the polycrystalline silicon at improving the RFperformance. In view thereof, in some preferred embodiments, the singlecrystal semiconductor handle substrate for use in the manufacture of anSOI structure according to the present invention may have resistivity inthe range of about 1,000 ohm-cm and about 6,000 Ohm-cm to achievesuperior HD2/HD3 suppression. The handle substrate comprises anepitaxial layer having a target resistivity within the range of betweenabout 100 ohm-cm and about 5000 ohm-cm, such as between about 200 ohm-cmand about 2000 ohm-cm, such as between about 400 ohm-cm and about 1000ohm-cm. The target resistivity is the measured resistivity of the layerwithout depletion, which is typically obtained for a layer grown on asubstrate of the same type, e.g., N-type epitaxial layer on n-typesubstrate or p-type epitaxial layer on p-type substrate. According tosome embodiments of the present invention, the epitaxial layer isdeposited with electrically active dopants of opposite type compared tothe substrate, e.g., the substrate may comprise p-type dopants, whilethe epitaxial layer is deposited with an n-type dopant or the substratemay comprise n-type dopants, while the epitaxial layer is deposited withan p-type dopant. By doping the epitaxial layer with a dopant of theopposite type, the epitaxial layer may be depleted by the opposite typesubstrate. That is, the epitaxial layer doped with n-type dopant may bedepleted by the p-type substrate, or the epitaxial layer doped withp-type dopant may be depleted by the n-type substrate. Accordingly, theepitaxial layer has an apparent resistivity that is much higher than thetarget resistivity. The apparent resistivity is the measured resistivityof a given sample, such as the engineered case in FIG. 4 where the 5micrometer thick n-type epitaxial silicon layer is depleted by thep-type substrate. Since the carriers in the epitaxial layer aredepleted, the measured resistivity is more than 10 times higher.

The epitaxial layer is grown with controlled thickness and targetresistivity so that it is fully depleted, leading to a high apparentresistivity. The apparent high resistivity leads to enhanced RFperformance, as depicted in FIG. 5, which depicts the reduction insecond harmonic distortion. Advantageously, handle substrates having alower range of resistivity may be used in RF devices, therebyeliminating process and metrology issues associated with UHR substrates.

I. Semiconductor Handle Substrate and Semiconductor Donor Substrate

The substrates for use in the present invention include a semiconductorhandle substrate, e.g., a single crystal semiconductor handle wafer anda semiconductor donor substrate, e.g., a single crystal semiconductordonor wafer. The semiconductor device layer in asemiconductor-on-insulator composite structure is derived from thesingle crystal semiconductor donor wafer. The semiconductor device layermay be transferred onto the semiconductor handle substrate by waferthinning techniques such as etching a semiconductor donor substrate orby cleaving a semiconductor donor substrate comprising a damage plane.

FIGS. 3A through 3E depict a process flow according to some embodimentsof the present invention. With reference to FIG. 3A, an exemplary,non-limiting single crystal semiconductor handle wafer 100 is depicted.In general, the single crystal semiconductor handle wafer 100 comprisestwo major, generally parallel surfaces. One of the parallel surfaces isa front surface 102 of the single crystal semiconductor handle wafer100, and the other parallel surface is a back surface 104 of the singlecrystal semiconductor handle wafer 100. The single crystal semiconductorhandle wafer 100 comprises a circumferential edge 106 joining the frontand back surfaces 102, 104. The single crystal semiconductor handlewafer 100 comprise a central axis 108 perpendicular to the two major,generally parallel surfaces 102, 104 and also perpendicular to a centralplane defined by the points midway between the front and back surfaces102, 104. The single crystal semiconductor handle wafer 100 comprises abulk region 110 between the two major, generally parallel surfaces 102,104. Since semiconductor wafers, e.g., silicon wafers, typically havesome total thickness variation (TTV), warp, and bow, the midpointbetween every point on the front surface 102 and every point on the backsurface 104 may not precisely fall within a plane. As a practicalmatter, however, the TTV, warp, and bow are typically so slight that toa close approximation the midpoints can be said to fall within animaginary central plane which is approximately equidistant between thefront and back surfaces 102, 104.

Prior to any operation as described herein, the front surface 102 andthe back surface 104 of the single crystal semiconductor handle wafer100 may be substantially identical. A surface is referred to as a “frontsurface” or a “back surface” merely for convenience and generally todistinguish the surface upon which the operations of method of thepresent invention are performed. In the context of the presentinvention, a “front surface” of a single crystal semiconductor handlewafer 100, e.g., a single crystal silicon handle wafer, refers to themajor surface of the substrate that becomes an interior surface of thebonded structure. Accordingly, a “back surface” of a single crystalsemiconductor handle wafer 100, e.g., a handle wafer, refers to themajor surface that becomes an exterior surface of the bonded structure.Similarly, a “front surface” of a single crystal semiconductor donorsubstrate, e.g., a single crystal silicon donor wafer, refers to themajor surface of the single crystal semiconductor donor substrate thatbecomes an interior surface of the bonded structure, and a “backsurface” of a single crystal semiconductor donor substrate, e.g., asingle crystal silicon donor wafer, refers to the major surface thatbecomes an exterior surface of the bonded structure. In the context ofthe present invention, one or more insulating layers may be prepared onthe front surfaces of either or both the single crystal semiconductorhandle substrate 100 and the single crystal semiconductor donorsubstrate. Upon completion of conventional bonding and wafer thinningsteps, the single crystal semiconductor donor substrate forms thesemiconductor device layer of the semiconductor-on-insulator (e.g.,silicon-on-insulator) composite structure.

The single crystal semiconductor handle substrate and the single crystalsemiconductor donor substrate may be single crystal semiconductorwafers. In preferred embodiments, the semiconductor wafers comprise amaterial selected from the group consisting of silicon, silicon carbide,silicon germanium, gallium arsenide, gallium nitride, indium phosphide,indium gallium arsenide, germanium, and combinations thereof. The singlecrystal semiconductor wafers, e.g., the single crystal silicon handlewafer and single crystal silicon donor wafer, of the present inventiontypically have a nominal diameter of at least about 150 mm, at leastabout 200 mm, at least about 300 mm, or at least about 450 mm. Waferthicknesses may vary from about 250 micrometers to about 1500micrometers, such as between about 300 micrometers and about 1000micrometers, suitably within the range of about 500 micrometers to about1000 micrometers. In some specific embodiments, the wafer thickness maybe about 725 micrometers. In some embodiments, the wafer thickness maybe about 775 micrometers.

In particularly preferred embodiments, the single crystal semiconductorwafers comprise single crystal silicon wafers which have been slicedfrom a single crystal ingot grown in accordance with conventionalCzochralski crystal growing methods or float zone growing methods. Suchmethods, as well as standard silicon slicing, lapping, etching, andpolishing techniques are disclosed, for example, in F. Shimura,Semiconductor Silicon Crystal Technology, Academic Press, 1989, andSilicon Chemical Etching, (J. Grabmaier ed.) Springer-Verlag, N.Y., 1982(incorporated herein by reference). Preferably, the wafers are polishedand cleaned by standard methods known to those skilled in the art. See,for example, W. C. O'Mara et al., Handbook of Semiconductor SiliconTechnology, Noyes Publications. If desired, the wafers can be cleaned,for example, in a standard SC1/SC2 solution. In some embodiments, thesingle crystal silicon wafers of the present invention are singlecrystal silicon wafers which have been sliced from a single crystalingot grown in accordance with conventional Czochralski (“Cz”) crystalgrowing methods, typically having a nominal diameter of at least about150 mm, at least about 200 mm, at least about 300 mm, or at least about450 mm. Preferably, both the single crystal silicon handle wafer and thesingle crystal silicon donor wafer have mirror-polished front surfacefinishes that are free from surface defects, such as scratches, largeparticles, etc. Wafer thickness may vary from about 250 micrometers toabout 1500 micrometers, such as between about 300 micrometers and about1000 micrometers, suitably within the range of about 500 micrometers toabout 1000 micrometers. In some specific embodiments, the waferthickness may be between about 725 micrometers and about 800micrometers, such as between about 750 micrometers and about 800micrometers. In some embodiments, the wafer thickness may be about 725micrometers. In some embodiments, the wafer thickness may be about 775micrometers.

In some embodiments, the single crystal semiconductor wafers, i.e.,single crystal semiconductor handle wafer and single crystalsemiconductor donor wafer, comprise interstitial oxygen inconcentrations that are generally achieved by the Czochralski-growthmethod. In some embodiments, the single crystal semiconductor waferscomprise oxygen in a concentration between about 4 PPMA and about 18PPMA. In some embodiments, the semiconductor wafers comprise oxygen in aconcentration between about 10 PPMA and about 35 PPMA. In someembodiments, the single crystal silicon wafer comprises oxygen in aconcentration of no greater than about 10 PPMA. Interstitial oxygen maybe measured according to SEMI MF 1188-1105.

The single crystal semiconductor handle wafer 100 may have anyresistivity obtainable by the Czochralski or float zone methods.Accordingly, the resistivity of the single crystal semiconductor handlewafer 100 is based on the requirements of the end use/application of thestructure of the present invention. The resistivity may therefore varyfrom milliohm or less to megaohm or more. In some embodiments, thesingle crystal semiconductor handle wafer 100 comprises a p-type or ann-type dopant. Suitable dopants include boron (p type), gallium (ptype), phosphorus (n type), antimony (n type), and arsenic (n type). Thedopant concentration is selected based on the desired resistivity of thehandle wafer. In some embodiments, the single crystal semiconductorhandle substrate comprises a p-type dopant. In some embodiments, thesingle crystal semiconductor handle substrate is a single crystalsilicon wafer comprising a p-type dopant, such as boron.

In some embodiments, the single crystal semiconductor handle wafer 100has a relatively low minimum bulk resistivity, such as below about 100ohm-cm, below about 50 ohm-cm, below about 1 ohm-cm, below about 0.1ohm-cm, or even below about 0.01 ohm-cm. In some embodiments, the singlecrystal semiconductor handle substrate 100 has a relatively low minimumbulk resistivity, such as below about 100 ohm-cm, or between about 1ohm-cm and about 100 ohm-cm. Low resistivity wafers may compriseelectrically active dopants, such as boron (p type), gallium (p type),aluminum (p type), indium (p type), phosphorus (n type), antimony (ntype), and arsenic (n type).

In some embodiments, the single crystal semiconductor handle wafer 100has a relatively high minimum bulk resistivity. High resistivity wafersare generally sliced from single crystal ingots grown by the Czochralskimethod or float zone method. High resistivity wafers may compriseelectrically active dopants, such as boron (p type), gallium (p type),aluminum (p type), indium (p type), phosphorus (n type), antimony (ntype), and arsenic (n type), in generally very low concentrations.Cz-grown silicon wafers may be subjected to a thermal anneal at atemperature ranging from about 600° C. to about 1000° C. in order toannihilate thermal donors caused by oxygen that are incorporated duringcrystal growth. In some embodiments, the single crystal semiconductorhandle wafer has a minimum bulk resistivity of at least 100 Ohm-cm, oreven at least about 500 Ohm-cm, such as between about 100 Ohm-cm andabout 100,000 Ohm-cm, or between about 500 Ohm-cm and about 100,000Ohm-cm, or between about 1000 Ohm-cm and about 100,000 Ohm-cm, orbetween about 500 Ohm-cm and about 10,000 Ohm-cm, or between about 750Ohm-cm and about 10,000 Ohm-cm, between about 1000 Ohm-cm and about10,000 Ohm-cm, between about 1000 Ohm-cm and about 6000 ohm-cm, betweenabout 2000 Ohm-cm and about 10,000 Ohm-cm, between about 3000 Ohm-cm andabout 10,000 Ohm-cm, or between about 3000 Ohm-cm and about 5,000Ohm-cm. In some preferred embodiments, the single crystal semiconductorhandle substrate has a bulk resistivity between about 1000 Ohm-cm andabout 6,000 Ohm-cm. Methods for preparing high resistivity wafers areknown in the art, and such high resistivity wafers may be obtained fromcommercial suppliers, such as SunEdison Semiconductor Ltd. (St. Peters,Mo.; formerly MEMC Electronic Materials, Inc.).

In some preferred embodiments, the single crystal semiconductor handlesubstrate comprises an electrically active dopant selected from thegroup consisting of boron, aluminum, gallium, indium, and anycombination thereof. In some preferred embodiments, the single crystalsemiconductor handle substrate comprises boron, which may be present ina concentration less than about 2×10¹³ atoms/cm³, less than about 1×10¹³atoms/cm³, such as less than about 5×10¹² atoms/cm³, or less than about1×10¹² atoms/cm³. Methods for preparing high resistivity wafers areknown in the art, and such high resistivity wafers may be obtained fromcommercial suppliers, such as SunEdison Semiconductor Ltd. (St. Peters,Mo.; formerly MEMC Electronic Materials, Inc.).

The single crystal semiconductor handle wafer 100 may comprise singlecrystal silicon. The single crystal semiconductor handle wafer 100 mayhave, for example, any of (100), (110), or (111) crystal orientation,and the choice of crystal orientation may be dictated by the end use ofthe structure.

Optionally, the front surface 102, the back surface 104, or both may beoxidized according to methods known in the art. Oxidation may beaccomplished by means known in the art, such as thermal oxidation (inwhich some portion of the deposited semiconductor material film will beconsumed) or CVD oxide deposition. The oxidation layer on the frontsurface 102, the back surface 104, or both may be at least about 1nanometer thick, such as between about 10 nanometers and about 5000nanometers thick, such as between about 100 nanometers and about 1000nanometers, or between about 200 nanometers and about 400 nanometers. Insome embodiments, the oxidation layer is relatively thin, such asbetween about 5 angstroms and about 25 angstroms, such as between about10 angstroms and about 15 angstroms. Thin oxide layers can be obtainedby exposure to a standard cleaning solution, such as an SC1/SC2 cleaningsolution. In some embodiments, the SC1 solution comprises 5 partsdeioinized water, 1 part aqueous NH₄OH (ammonium hydroxide, 29% byweight of NH₃), and 1 part of aqueous H₂O₂ (hydrogen peroxide, 30%). Insome embodiments, the handle substrate may be oxidized by exposure to anaqueous solution comprising an oxidizing agent, such as an SC2 solution.In some embodiments, the SC2 solution comprises 5 parts deioinizedwater, 1 part aqueous HCl (hydrochloric acid, 39% by weight), and 1 partof aqueous H₂O₂ (hydrogen peroxide, 30%).

II. Epitaxial Deposition

According to the method of the present invention, and with reference toFIGS. 3A and 3B, an epitaxial layer 200 is deposited by an epitaxialmethod upon the front surface 102 of the starting single crystalsemiconductor handle substrate 100.

The epitaxial layer 200 may be deposited upon the front surface 102 ofthe starting single crystal semiconductor handle substrate 100 by avapor phase epitaxial method or a liquid phase epitaxial method. Forexample, the epitaxial layer 200 may be deposited using metalorganicchemical vapor deposition (MOCVD), physical vapor deposition (PVD),chemical vapor deposition (CVD), low pressure chemical vapor deposition(LPCVD), plasma enhanced chemical vapor deposition (PECVD), molecularbeam epitaxy (MBE), or liquid phase epitaxy (LPE). Epitaxial depositionresults in a semiconductor layer having the same underlying crystallinestructure as the starting single crystal semiconductor handle substrate100. For example, a single crystal silicon handle substrate 100 may havecrystal orientations for (100), (100), and (110). In some embodiments,the single crystal silicon handle substrate 100 may have (100) crystalorientation. The epitaxial layer 200 conforms to the crystal orientationof the underlying substrate 100. Accordingly, in some embodiments, thesingle crystal silicon handle substrate 100 and the epitaxial layer 200have (100) crystal orientation. A suitable reactor for epitaxialdeposition is an ASM or an Applied Materials commercial epi reactor. Thereaction conditions for epitaxial deposition include a temperatureranging from between about 600° C. and about 1100° C., at a pressurebetween about 1 Torr and about 760 Torr, such as between about 10 Torrand about 760 Torr. Hydrogen (H₂) is a suitable carrier gas at a flowrate of between about 10 slm and about 200 slm.

Silicon precursors for a vapor phase epitaxial method include methylsilane, silicon tetrahydride (silane), trisilane, disilane, pentasilane,neopentasilane, tetrasilane, dichlorosilane (SiH₂Cl₂), trichlorosilane(SiHCl₃), silicon tetrachloride (SiCl₄), among others. The overallthickness of the epitaxial layer 200 comprising silicon may be betweenabout 0.2 micrometers and about 20 micrometers thick, or between about0.5 micrometers and about 10 micrometers thick, such as between about 5micrometers and about 10 micrometers thick. Silicon doped with carbonmay be deposited by thermal plasma chemical vapor deposition inepitaxial reactors using precursors such as silicon tetrachloride andmethane. Suitable carbon precursors for CVD or PECVD includemethylsilane, methane, ethane, ethylene, among others. For LPCVDdeposition, methylsilane is a particularly preferred precursor since itprovides both carbon and silicon. For PECVD deposition, the preferredprecursors include silane and methane. In some embodiments, theepitaxial layer 200 comprises silicon doped with carbon at a carbonconcentration between about 0.1 mole % and about 5 mole %, or betweenabout 0.5 mole % and about 2 mole %. The overall thickness of theepitaxial layer 200 comprising silicon doped with carbon may betweenabout 0.1 micrometers and about 20 micrometers thick, such as betweenabout 0.1 micrometers and about 10 micrometers thick, such as betweenabout 5 micrometers and about 10 micrometers thick.

In some embodiments, the epitaxial layer 200 may comprise anelectrically active dopant. The dopant may be p-type such as boron (ptype), gallium (p type), aluminum (p type), indium (p type) or n-typesuch as phosphorus (n type), antimony (n type), and arsenic (n type). Adopant may be incorporated into the epitaxial layer 200 by including anappropriate precursor gas, such as a boron precursor (e.g., by includingdiborane (B₂H₆) in the reaction gas mixture), an arsenic precursor(e.g., by include arsine (ArH₃) in the reaction gas mixture), aphosphorus precursor (e.g., by include phosphine (PH₃) in the reactiongas mixture), and an antimony precursor (e.g., by including dimericantimony in the reaction gas mixture). The resistivity of the epitaxiallayer may range from between about 100 ohm-cm and about 5000 ohm-cm,such as between about 200 ohm-cm and about 2000 ohm-cm, such as betweenabout 400 ohm-cm and about 1000 ohm-cm. Accordingly, the concentrationof an electrically active dopant in the epitaxial layer may be less thanabout 1×10¹⁴ atoms/cm³, less than about 1×10¹³ atoms/cm³, such as lessthan about 5×10¹² atoms/cm³.

In some embodiments, the epitaxial layer 200 may be doped withelectrically active dopants of opposite type than the electricallyactive dopant within the single crystal semiconductor handle substrate100 and. In some embodiments, the single crystal semiconductor handlesubstrate comprises an electrically active p-type dopant (e.g., boron (ptype), gallium (p type), aluminum (p type), indium (p type)) at aconcentration of less than about 2×10¹³ atoms/cm³, less than about1×10¹³ atoms/cm³, such as less than about 5×10¹² atoms/cm³, or less thanabout 1×10¹² atoms/cm³. In some embodiments, the concentration of theelectrically active p-type dopant (e.g., boron (p type), gallium (ptype), aluminum (p type), indium (p type)) may be at least about 1×10¹²atoms/cm³, such as at least about 2×10¹² atoms/cm³. These concentrationsgenerally correspond to a resistivity within the range of about 1000ohm-cm and about 6000 ohm-cm. The epitaxial layer may comprise anelectrically active n-type dopant (e.g., phosphorus (n type), antimony(n type), and arsenic (n type)) at a concentration of less than about1×10¹⁴ atoms/cm³, less than about 1×10¹³ atoms/cm³, such as less thanabout 5×10¹² atoms/cm³. In some embodiments, the concentration of theelectrically active n-type dopant (e.g., phosphorus (n type), antimony(n type), and arsenic (n type)) is at least about 1×10¹² atoms/cm³, suchas at least about 2×10¹² atoms/cm³. These concentrations generallycorrespond to a resistivity within the range between about 100 ohm-cmand about 5000 ohm-cm, such as between about 200 ohm-cm and about 2000ohm-cm, such as between about 400 ohm-cm and about 1000 ohm-cm. Thecombination of the epitaxial layer dopant type, the epitaxial layerresistivity, and the epitaxial layer thickness, and the dopant type andresistivity of the handle substrate results in an epitaxial layer thatis fully depleted. As a result, the epitaxial layer achieves an apparentresistivity of greater than about 5000 Ohm-cm, or even greater thanabout 10,000 Ohm-cm. See FIG. 4, which demonstrates the effect of themultilayer structure of the present invention compared to a controlstructure. FIG. 4 is a graph demonstrating the higher apparentresistivity of semiconductor material layered upon a substrate accordingto a structure of the present invention (engineered sample) compared tothe the lower resistivity of semiconductor material layered upon asubstrate according to the conventional method (control sample).

III. Deposition of Charge Trapping Layer

According to the method of the present invention and with reference toFIGS. 3B and 3C, a charge trapping layer 300 is deposited on theepitaxial layer 200. In some embodiments, the charge trapping layer 300comprises polycrystalline silicon. Such materials includepolycrystalline semiconductor materials and amorphous semiconductormaterials. Materials that may be polycrystalline or amorphous includesilicon (Si), silicon germanium (SiGe), silicon doped with carbon (SiC),and germanium (Ge). Polycrystalline semiconductor, e.g., polycrystallinesilicon, denotes a material comprising small silicon crystals havingrandom crystal orientations. Polycrystalline material denotes a materialcomprising small crystals having random crystal orientations.Polycrystalline grains may be as small in size as about 20 nanometers,and the grain size generally ranges from between about 20 nanometers andabout 1 micrometer, such as between about 0.3 micrometer and about 1micrometer. According to the method of the present invention, thesmaller the crystal grain size of polycrystalline material deposited thehigher the defectivity in the charge trapping layer. The resistivity ofthe polycrystalline silicon charge trapping layer may be at least 100Ohm-cm, at least about 500 Ohm-cm, at least about 1000 Ohm-cm, at leastabout 3000 Ohm-cm, or even at least about 7000 ohm-cm, such as betweenabout 100 Ohm-cm and about 100,000 Ohm-cm, or between about 500 Ohm-cmand about 100,000 Ohm-cm, or between about 1000 Ohm-cm and about 100,000Ohm-cm, or between about 500 Ohm-cm and about 100,000 Ohm-cm, or betweenabout 750 Ohm-cm and about 100,000 Ohm-cm. In some preferredembodiments, the resistivity of the polycrystalline silicon layer isbetween about 3000 Ohm-cm and about 100,000 Ohm-cm, such as betweenabout 3000 Ohm-cm and about 10,000 Ohm-cm or even between about 7000ohm-cm and about 100,000 ohm-cm, such as between about 7000 ohm-cm andabout 10,000 ohm-cm.

The material for deposition of the charge trapping layer 300 onto theepitaxial layer 200 may be deposited by vapor deposition. The materialfor deposition of the charge trapping layer 300 onto the epitaxial layer200 may be deposited by chemical or physical vapor deposition, forexample, by metalorganic chemical vapor deposition (MOCVD), physicalvapor deposition (PVD), chemical vapor deposition (CVD), low pressurechemical vapor deposition (LPCVD), or plasma enhanced chemical vapordeposition (PECVD). In preferred embodiments, polycrystalline silicon isdeposited by CVD. Silicon precursors for CVD include methyl silane,silicon tetrahydride (silane), trisilane, disilane, pentasilane,neopentasilane, tetrasilane, dichlorosilane (SiH₂Cl₂), trichlorosilane(SiHCl₃), silicon tetrachloride (SiCl₄), among others. In some preferredembodiments, the silicon precursor is selected from among silane,dichlorosilane (SiH₂Cl₂), and trichlorosilane (SiHCl₃). For example,polycrystalline silicon may be deposited onto the surface oxidationlayer by CVD of silane, dichlorosilane (SiH₂Cl₂), and trichlorosilane(SiHCl₃) in a temperature greater than about 850° C., such as betweenabout 850° C. and about 1100° C., or between about 850° C. and about1000° C. The high temperature contributes, among other advantages, highgrowth rate, thereby contributing to throughput and cost reduction. CVDdeposition rates may range be at least about 0.1 micrometer/minute, suchas between about 0.1 micrometer/minute to about 10 micrometers/minute,or between about 0.1 micrometer/minute to about 2 micrometers/minute.Deposition of the polycrystalline silicon layer may continue until thelayer has a thickness of at least about 0.1 micrometer, such as betweenabout 0.1 micrometer and about 50 micrometers, such as between about 0.1micrometer and about 20 micrometers, between about 0.1 micrometer andabout 10 micrometers, between about 0.5 micrometer and about 5micrometers, or between about 0.5 micrometer and about 3 micrometers,such as between about 1 micrometer and about 2 micrometers or betweenabout 2 micrometers and about 5 micrometers. Deposition may occur at apressure between about 1 Torr and about 760 Torr, such as between about1 Torr and about 400 Torr.

In some embodiments, deposition of the polycrystalline silicon layer bychemical vapor deposition is interrupted after deposition of apolycrystalline silicon seed layer. The polycrystalline silicon seedlayer may have a thickness less than the overall desired thickness ofthe final polycrystalline silicon charge trapping layer. Accordingly,the polycrystalline seed layer may be deposited to a thickness of lessthan 20 micrometers, less than 10 micrometers, less than 5 micrometers,less than 3 micrometers, less than 2 micrometers, or less than 1micrometer, or less than 0.5 micrometer, such as between about 50nanometers and about 20 micrometers, or between about 50 nanometers andabout 10 micrometers, or between about 50 nanometers and about 5micrometers, or between about 50 nanometers and about 3 micrometers, orbetween about 50 nanometers and about 2 micrometers, or between about 50nanometers and about 1 micrometers, or between about 50 nanometers andabout 500 nanometers, or between about 50 nanometers and about 200nanometers. The thickness of the seed layer is set by the size of thepolysilicon nuclei. To achieve effective stress release, the seed layerneeds to cover the surface of the underlying layer while leaving voidssmaller than 50 nm, which enables the access of H₂ to the interfacebetween the polysilicon seed layer and the underlying layer. H₂ reducesinterfacial oxide and promotes the diffusion of the atoms at the grainboundaries of the polysilicon seed layer to the substrate and thusreleases the film stress. When the seed layer is thick enough tocompletely prevent H₂ access to the underlying layer, the subsequentannealing process is not able to release the film stress effectively. Onthe other hand, when the seed layer is not continuous and the openingarea between two adjacent nuclei is wider than 50 nm, large nuclei areformed during the seed annealing process. The large nuclei will growinto large grains (i.e., diameter >1 um) at the end of polysilicondeposition, which reduces the trapping efficiency. Deposition may beinterrupted by ceasing the flow of silicon precursors into the CVDchamber. After interruption of the deposition of polycrystallinesilicon, the handle substrate comprising the polycrystalline seed layermay be annealed. Annealing the polycrystalline seed layer contributes todesirable charge trapping layer properties, such as obtaining a cleansurface, a high purity film, a high resistivity film, desired nucleisize and uniformity, and reduction of residual film stress. In someembodiments, the polycrystalline silicon seed layer is subjected to ahigh temperature anneal in order to reduce film stress to a rangebetween about 0 MPa and about 500 MPa, such as between about 0 MPa andabout 100 MPa. The polycrystalline seed layer is annealed at atemperature greater than about 1000° C., such as between about 1000° C.and about 1200° C., or between about 1000° C. and about 1100° C. Theseed layer may be annealed for a duration between about 1 second andabout 300 seconds, such as between about 5 seconds and about 60 seconds,or between about 10 seconds and about 40 seconds. The ambient atmospherefor anneal may comprise hydrogen, hydrogen chloride, chlorine, or anycombination of hydrogen, hydrogen chloride, and chlorine. The annealingstep can be performed at reduced pressure or atmospheric pressure, suchas between about 1 Torr and about 760 Torr, or between about 10 Torr andabout 760 Torr. The grain size and the stress of the polycrystallinesilicon film is controlled by the annealing temperature, duration, andgas flow. After the appropriate anneal duration, deposition by chemicalvapor deposition of the polycrystalline silicon layer is resumed aftercooling the single crystal semiconductor handle substrate to atemperature between about 850° C. and about 1000° C.

In some embodiments, the single crystal semiconductor handle substrate100 comprising the epitaxial layer 200 and the polycrystalline siliconcharge trapping layer 300 is annealed after deposition is complete.Annealing the polycrystalline layer contributes to desirable chargetrapping layer properties, such as obtaining a clean surface, a highpurity film, a high resistivity film, desired nuclei size anduniformity, and reduction of residual film stress. In some embodiments,the fully deposited polycrystalline silicon charge trapping layer issubjected to a high temperature anneal in order to reduce film stress toa range between about 0 MPa and about 500 MPa, such as between about 0MPa and about 100 MPa. The handle substrate 100 comprising the epitaxiallayer 200 and the polycrystalline silicon charge trapping layer 300 maybe annealed at a temperature greater than about 1000° C., such asbetween about 1000° C. and about 1100° C. The handle substrate 100comprising the epitaxial layer 200 and the polycrystalline siliconcharge trapping layer 300 may be annealed for a duration between about 1second and about 300 seconds, such as between about 5 seconds and about60 seconds, or between about 10 seconds and about 40 seconds. Theambient atmosphere for anneal may comprise hydrogen, hydrogen chloride,chlorine, or any combination of hydrogen, hydrogen chloride, andchlorine. After the appropriate anneal duration, the CVD chamber may becooled to a temperature safe for removal single crystal semiconductorhandle substrate.

In some embodiments, an insulating or dielectric layer may be formed ontop of the deposited charge trapping layer 300. The insulating layer maycomprise a semiconductor oxide, a semiconductor nitride, or asemiconductor oxynitride. The dielectric layer according to the presentinvention may comprise insulating materials selected from among silicondioxide, silicon nitride, silicon oxynitride, hafnium oxide, titaniumoxide, zirconium oxide, lanthanum oxide, barium oxide, and anycombination thereof. In some embodiments, the dielectric layer comprisesone or more insulating material selected from the group consisting ofsilicon dioxide, silicon nitride, silicon oxynitride, and anycombination thereof. The dielectric layer may comprise two insulatinglayers, three insulating layers, or more. Each insulating layer maycomprise a material selected from among silicon dioxide, siliconoxynitride, silicon nitride, hafnium oxide, titanium oxide, zirconiumoxide, lanthanum oxide, barium oxide, and any combination thereof. Insome embodiments, each insulating layer may comprise a material selectedfrom the group consisting of silicon dioxide, silicon nitride,siliconoxynitride, and any combination thereof. In some embodiments, thedielectric layer comprises three insulating layers. In some embodiments,the three insulating layers comprise a silicon dioxide layer, a siliconnitride layer in interfacial contact with the silicon dioxide layer, anda silicon dioxide layer in interfacial contact with the silicon nitridelayer.

Deposition of the insulating layer may be accomplished by means known inthe art, such as thermal oxidation (in which some portion of thedeposited semiconductor material film will be consumed) and/or CVD oxideand/or nitride deposition. In some embodiments, the charge trappinglayer may be thermally oxidized (in which some portion of the depositedsemiconductor material film will be consumed) or the film may be grownby CVD oxide and/or nitride deposition. In some embodiments, the chargetrapping layer may be thermally oxidized in a furnace such as an ASMA400. The temperature may range from 750° C. to 1200° C. in an oxidizingambient. The oxidizing ambient atmosphere can be a mixture of inert gas,such as Ar or N₂, and O₂. The oxygen content may vary from 1 to 10percent, or higher. In some embodiments, the oxidizing ambientatmosphere may be up to 100% (a “dry oxidation”). In some embodiments,the ambient atmosphere may comprise a mixture of inert gas, such as Aror N₂, and oxidizing gases, such as O₂ and water vapor (a “wetoxidation”). In an exemplary embodiment, semiconductor handle wafers maybe loaded into a vertical furnace, such as an A400. The temperature isramped to the oxidizing temperature with a mixture of N₂ and O₂. Afterthe desired oxide thickness has been obtained, the O₂ is turned off andthe furnace temperature is reduced and wafers are unloaded from thefurnace. In order to incorporate nitrogen in the interfacial layer todeposit silicon nitride or silicon oxynitride, the atmosphere maycomprise nitrogen alone or a combination of oxygen and nitrogen, and thetemperature may be increased to a temperature between 1100° C. and 1400°C. An alternative nitrogen source is ammonia. In some embodiments, thecharge trapping layer may be treated for a duration sufficient toprovide an insulating layer of between about 2000 angstroms and about10,000 angstroms thickness.

After deposition of the charge trapping layer 300, and optionaldeposition of an insulating layer, wafer cleaning and polishing isoptional. In some embodiments, the deposited polycrystalline siliconcharge trapping layer has a surface roughness as measured byRMS_(2×2 um2) on the order of 50 nanometers. If desired, the wafers canbe cleaned, for example, in a standard SC1/SC2 solution. Additionally,the wafers, particularly, the charge trapping layer or the optionalinsulating layer, may be subjected to chemical mechanical polishing(CMP) to reduce the surface roughness, preferably to the level ofRMS_(2×2 um2) is less than about 5 angstroms, preferably less than about2 angstroms, such as between about 1 angstrom and about 2 angstroms,wherein root mean squared—

$R_{q} = \sqrt{\frac{1}{n}{\sum\limits_{i = 1}^{n}y_{i}^{2}}}$

The roughness profile contains ordered, equally spaced points along thetrace, and y_(i) is the vertical distance from the mean line to the datapoint. At a surface roughness of preferably less than 2 angstroms, thesurface is ready for bonding.

IV. Plasma Activation

In some embodiments, the single crystal semiconductor handle substrate100 comprising the epitaxial layer 200 and the polycrystalline siliconcharge trapping layer 300 is subjected to oxygen plasma and/or nitrogenplasma surface activation. In some embodiments, the oxygen plasma and/ornitrogen plasma surface activation tool is a commercially availabletool, such as those available from EV Group, such as EVG®810LT Low TempPlasma Activation System. The single crystal semiconductor handlesubstrate 100 comprising the epitaxial layer 200 and the polycrystallinesilicon charge trapping layer 300 is loaded into the chamber. Thechamber is evacuated and backfilled with an oxygen gas source and/or anitrogen gas source in a carrier gas, such as argon, to a pressure lessthan atmospheric to thereby create the plasma. Oxygen and/or water aresuitable source gases for plasma oxide treatment. Ammonia and/ornitrogen and/or nitric oxide (NO) and/or nitrous oxide (N₂O) gas aresuitable source gases for plasma nitride treatment. Oxynitride plasmafilms may be deposited by including oxygen and nitrogen gas sources.Additionally, the use of nitric oxide or nitrous oxide additionallyincorporates oxygen in to the insulating layer, thereby depositing anoxynitride film. To deposit a silicon nitride or a silicon oxide plasmafilm, suitable silicon precursors include methyl silane, silicontetrahydride (silane), trisilane, disilane, pentasilane, neopentasilane,tetrasilane, dichlorosilane (SiH₂Cl₂), trichlorosilane (SiHCl₃), silicontetrachloride (SiCl₄), among others. Suitably, Ar is added as a carriergas.

The single crystal semiconductor handle substrate 100 is exposed to thisplasma for the desired time, which may range from about 1 second toabout 120 seconds, in order to grow a thin oxide, nitride, or oxynitridelayer. The oxide, nitride, or oxynitride layer may have a thicknessranging from about 10 angstroms to about 100 angstroms. This nitridelayer can act as an effective diffusion barrier to prevent diffusion ofcontaminants trapped at the bond interface from diffusing in and throughthe Poly Silicon trap layer. Plasma surface activation is performed inorder to render the surface of the charge trapping layer 300 or thesurface of the optional insulating layer hydrophilic and amenable tobonding to a single crystal semiconductor donor substrate. After plasmaactivation, the activated surface is rinsed with deionized water. Thewafer is then spun dry prior to bonding.

V. Preparation of the Bonded Structure

With reference to FIG. 3D, the high resistivity single crystalsemiconductor handle substrate 100, e.g. a single crystal semiconductorhandle wafer such as a single crystal silicon handle wafer, preparedaccording to the method described herein comprising the epitaxial layer200 and the polycrystalline silicon charge trapping layer 300 is nextbonded to a semiconductor donor substrate 400, e.g., a single crystalsemiconductor donor wafer, which is prepared according to conventionallayer transfer methods. The single crystal semiconductor donor substrate400 may be a single crystal semiconductor wafer. In preferredembodiments, the semiconductor wafer comprises a material selected fromthe group consisting of silicon, silicon carbide, silicon germanium,gallium arsenide, gallium nitride, indium phosphide, indium galliumarsenide, germanium, and combinations thereof. Depending upon thedesired properties of the final integrated circuit device, the singlecrystal semiconductor (e.g., silicon) donor wafer 400 may comprise adopant selected from among boron (p type), gallium (p type), aluminum (ptype), indium (p type), phosphorus (n type), antimony (n type), andarsenic (n type). The resistivity of the single crystal semiconductor(e.g., silicon) donor wafer may range from 1 to 50 Ohm-cm, typically,from 5 to 25 Ohm-cm. The single crystal semiconductor donor wafer 400may be subjected to standard process steps including oxidation, implant,and post implant cleaning. Accordingly, a semiconductor donor substrate400, such as a single crystal semiconductor wafer of a material that isconventionally used in preparation of multilayer semiconductorstructures, e.g., a single crystal silicon donor wafer, that has beenetched and polished and optionally oxidized, is subjected to ionimplantation to form a damage layer in the donor substrate.

In some embodiments, the semiconductor donor substrate 400 comprises adielectric layer 410. The dielectric layer 410 according to the presentinvention may comprise insulating materials selected from among silicondioxide, silicon nitride, silicon oxynitride, hafnium oxide, titaniumoxide, zirconium oxide, lanthanum oxide, barium oxide, and anycombination thereof. In some embodiments, the dielectric layer 410comprises one or more insulating layers comprising a material selectedfrom the group consisting of silicon dioxide, silicon nitride, siliconoxynitride, and any combination thereof. In some embodiments, thedielectric layer has a thickness of at least about 10 nanometer thick,such as between about 10 nanometers and about 10,000 nanometers, betweenabout 10 nanometers and about 5,000 nanometers, between 50 nanometersand about 400 nanometers, or between about 100 nanometers and about 400nanometers, such as about 50 nanometers, 100 nanometers, or 200nanometers.

In some embodiments, the dielectric layer 410 comprises multiple layersof insulating material. The dielectric layer may comprise two insulatinglayers, three insulating layers, or more. Each insulating layer maycomprise a material selected from among silicon dioxide, siliconoxynitride, silicon nitride, hafnium oxide, titanium oxide, zirconiumoxide, lanthanum oxide, barium oxide, and any combination thereof. Insome embodiments, each insulating layer may comprise a material selectedfrom the group consisting of silicon dioxide, silicon nitride,siliconoxynitride, and any combination thereof. Each insulating layermay have a thickness of at least about 10 nanometer thick, such asbetween about 10 nanometers and about 10,000 nanometers, between about10 nanometers and about 5,000 nanometers, between 50 nanometers andabout 400 nanometers, or between about 100 nanometers and about 400nanometers, such as about 50 nanometers, 100 nanometers, or 200nanometers.

In some embodiments, the front surface of the single crystalsemiconductor donor substrate 400 (e.g., a single crystal silicon donorsubstrate) may be thermally oxidized (in which some portion of thedeposited semiconductor material film will be consumed) to prepare thesemiconductor oxide film, or the semiconductor oxide (e.g., silicondioxide) film may be grown by CVD oxide deposition. In some embodiments,the front surface of the single crystal semiconductor donor substrate400 may be thermally oxidized in a furnace such as an ASM A400 in thesame manner described above. In some embodiments, the single crystalsemiconductor donor substrate 400 is oxidized to provide an oxide layeron the front surface layer of at least about 1 nanometer thick, about 10nanometer thick, such as between about 10 nanometers and about 10,000nanometers, between about 10 nanometers and about 5,000 nanometers, orbetween about 100 nanometers and about 400 nanometers. In someembodiments, the oxidation layer on the single crystal semiconductordonor substrate 400 is relatively thin, such as between about 5angstroms and about 25 angstroms, such as between about 10 angstroms andabout 15 angstroms. Thin oxide layers can be obtained by exposure to astandard cleaning solution, such as an SC1/SC2 cleaning solution.

Ion implantation may be carried out in a commercially availableinstrument, such as an Applied Materials Quantum II, a Quantum LEAP, ora Quantum X. Implanted ions include He, H, H₂, or combinations thereof.Ion implantation is carried out as a density and duration sufficient toform a damage layer in the semiconductor donor substrate. Implantdensity may range from about 10¹² ions/cm² to about 10¹⁷ ions/cm², suchas from about 10¹⁴ ions/cm² to about 10¹⁷ ions/cm², such as from about10¹⁵ ions/cm² to about 10¹⁶ ions/cm². Implant energies may range fromabout 1 keV to about 3,000 keV, such as from about 10 keV to about 3,000keV. Implant energies may range from about 1 keV to about 3,000 keV,such as from about 5 keV to about 1,000 keV, or from about 5 keV toabout 200 keV, or from 5 keV to about 100 keV, or from 5 keV to about 80keV. The depth of implantation determines the thickness of the singlecrystal semiconductor device layer in the final SOI structure. The ionsmay be implanted to a depth between about 100 angstroms and about 30,000angstroms, such as between about 200 angstroms and about 20,000angstroms, such as between about 2000 angstroms and about 15,000angstroms, or between about 15,000 angstroms and about 30,000 angstroms.In some embodiments it may be desirable to subject the single crystalsemiconductor donor wafers, e.g., single crystal silicon donor wafers,to a clean after the implant. In some preferred embodiments, the cleancould include a Piranha clean followed by a DI water rinse and SC1/SC2cleans.

In some embodiments of the present invention, the single crystalsemiconductor donor substrate 400 having an ion implant region thereinformed by He⁺, H⁺, H₂ ⁺, and any combination thereof ion implant isannealed at a temperature sufficient to form a thermally activatedcleave plane in the single crystal semiconductor donor substrate. Anexample of a suitable tool might be a simple Box furnace, such as a BlueM model. In some preferred embodiments, the ion implanted single crystalsemiconductor donor substrate is annealed at a temperature of from about200° C. to about 350° C., from about 225° C. to about 350° C.,preferably about 350° C. Thermal annealing may occur for a duration offrom about 2 hours to about 10 hours, such as from about 2 hours toabout 2 hours. Thermal annealing within these temperatures ranges issufficient to form a thermally activated cleave plane. After the thermalanneal to activate the cleave plane, the single crystal semiconductordonor substrate surface is preferably cleaned.

In some embodiments, the ion-implanted and optionally cleaned andoptionally annealed single crystal semiconductor donor substrate issubjected to oxygen plasma and/or nitrogen plasma surface activation. Insome embodiments, the oxygen plasma surface activation tool is acommercially available tool, such as those available from EV Group, suchas EVG®810LT Low Temp Plasma Activation System. The ion-implanted andoptionally cleaned single crystal semiconductor donor wafer is loadedinto the chamber. The chamber is evacuated and backfilled with O₂ or N₂to a pressure less than atmospheric to thereby create the plasma. Thesingle crystal semiconductor donor wafer is exposed to this plasma forthe desired time, which may range from about 1 second to about 120seconds. Oxygen or nitrogen plasma surface oxidation is performed inorder to render the front surface of the single crystal semiconductordonor substrate hydrophilic and amenable to bonding to a single crystalsemiconductor handle substrate prepared according to the methoddescribed above. After plasma activation, the activated surface isrinsed with deionized water. The wafer is then spun dry prior tobonding.

The hydrophilic front surface layer of the single crystal semiconductordonor substrate 400 and the front surface of single crystalsemiconductor handle substrate 100 comprising the epitaxial layer 200and the polycrystalline silicon charge trapping layer 300 are nextbrought into intimate contact to thereby form a bonded structure. Thebonded structure comprises a dielectric layer 410, e.g., a buried oxidesuch as silicon oxide.

Since the mechanical bond is relatively weak, the bonded structure isfurther annealed to solidify the bond between the single crystalsemiconductor donor substrate 400 and the single crystal semiconductorhandle substrate 100 comprising the epitaxial layer 200 and thepolycrystalline silicon charge trapping layer 300. In some embodimentsof the present invention, the bonded structure is annealed at atemperature sufficient to form a thermally activated cleave plane in thesingle crystal semiconductor donor substrate. An example of a suitabletool might be a simple Box furnace, such as a Blue M model. In somepreferred embodiments, the bonded structure is annealed at a temperatureof from about 200° C. to about 350° C., from about 225° C. to about 350°C., preferably about 350° C. Thermal annealing may occur for a durationof from about 0.5 hours to about 10 hour, preferably a duration of about2 hours. Thermal annealing within these temperatures ranges issufficient to form a thermally activated cleave plane. After the thermalanneal to activate the cleave plane, the bonded structure may becleaved.

In some embodiments, the anneal may occur at relatively high pressures,such as between about 0.5 MPa and about 200 MPa, such as between about0.5 MPa and about 100 MPa, such as between about 0.5 MPa and about 50MPa, or between about 0.5 MPa and about 10 MPa, or between about 0.5 MPaand about 5 MPa. In conventional bonding methods, the temperature islikely limited by the “autocleave”. This occurs when the pressure of theplatelets at the implant plane exceeds the external isostatic pressure.Accordingly, conventional anneal may be limited to bonding temperaturesbetween about 350° C. and about 400° C. because of autocleave. Afterimplantation and bond, the wafers are weakly held together. But the gapbetween the wafers is sufficient to prevent gas penetration or escape.Weak bonds can be strengthened by heat treatments, but the cavitiesformed during implant are filled with gas. While heating, the gas insidethe cavities pressurizes. It is estimated that the pressure may reach0.2-1 GPa (Cherkashin et al., J. Appl. Phys. 118, 245301 (2015)),depending on the dosage. When the pressure exceeds a critical value, thelayer delaminates. This is referred to as an autocleave or thermalcleave. It prevents higher temperature or longer time in the anneal.According to some embodiments of the present invention, bonding occursat elevated pressures, e.g., between about 0.5 MPa and about 200 MPa,such as between about 0.5 MPa and about 100 MPa, such as between about0.5 MPa and about 50 MPa, or between about 0.5 MPa and about 10 MPa, orbetween about 0.5 MPa and about 5 MPa, which thereby enables bonding atelevated temperatures. In some embodiments, the bonded structure isannealed at a temperature of from about 300° C. to about 700° C., fromabout 400° C. to about 600° C., such as between about 400° C. and about450° C., or even between about 450° C. and about 600° C., or betweenabout 350° C. and about 450° C. Increasing the thermal budget will havea positive effect on the bond strength. Thermal annealing may occur fora duration of from about 0.5 hours to about 10 hour, such as betweenabout 0.5 hours and about 3 hours, preferably a duration of about 2hours. Thermal annealing within these temperatures ranges is sufficientto form a thermally activated cleave plane. In conventional bondinganneals, the edge of both the handle wafer and donor wafer may becomefar apart due to the roll off. In this area, there is no layer transfer.It is called the terrace. Pressurized bonding is expected to reduce thisterrace, extending the SOI layer further out towards the edge. Themechanism is based on trapped pockets of air being compressed and“zippering” outwards. After the thermal anneal to activate the cleaveplane, the bonded structure may be cleaved.

After the thermal anneal, the bond between the single crystal singlecrystal semiconductor donor substrate 400 and the single crystalsemiconductor handle substrate 100 comprising the epitaxial layer 200and the polycrystalline silicon charge trapping layer 300 is strongenough to initiate layer transfer via cleaving the bonded structure atthe cleave plane. Cleaving may occur according to techniques known inthe art. In some embodiments, the bonded structure may be placed in aconventional cleave station affixed to stationary suction cups on oneside and affixed by additional suction cups on a hinged arm on the otherside. A crack is initiated near the suction cup attachment and themovable arm pivots about the hinge cleaving the wafer apart. Cleavingremoves a portion of the semiconductor donor wafer, thereby leaving asingle crystal semiconductor device layer 500, preferably a silicondevice layer, on the semiconductor-on-insulator composite structure. SeeFIG. 3E.

After cleaving, the cleaved structure may be subjected to a hightemperature anneal in order to further strengthen the bond between thetransferred device layer 500 and the single crystal semiconductor handlesubstrate 100 comprising the epitaxial layer 200 and the polycrystallinesilicon charge trapping layer 300. An example of a suitable tool mightbe a vertical furnace, such as an ASM A400. In some preferredembodiments, the bonded structure is annealed at a temperature of fromabout 1000° C. to about 1200° C., preferably at about 1000° C. Thermalannealing may occur for a duration of from about 0.5 hours to about 8hours, preferably a duration of about 2 to 4 hours. Thermal annealingwithin these temperatures ranges is sufficient to strengthen the bondbetween the transferred device layer and the single crystalsemiconductor handle substrate.

After the cleave and high temperature anneal, the bonded structure maybe subjected to a cleaning process designed to remove thin thermal oxideand clean particulates from the surface. In some embodiments, the singlecrystal semiconductor device layer may be brought to the desiredthickness and smoothness by subjecting to a vapor phase HCl etch processin a horizontal flow single wafer epitaxial reactor using H₂ as acarrier gas. In some embodiments, the semiconductor device layer 500 mayhave a thickness between about 10 nanometers and about 20 micrometers,between about 20 nanometers and about 3 micrometers, such as betweenabout 20 nanometers and about 2 micrometers, such as between about 20nanometers and about 1.5 micrometers or between about 1.5 micrometersand about 3 micrometers. Thick film device layers may have a devicelayer thickness between about 1.5 micrometers and about 20 micrometers.Thin film device layers may have a thickness between about 0.01micrometer and about 0.20 micrometer.

In some embodiments, an epitaxial layer may be deposited on thetransferred single crystal semiconductor device layer 500. A depositedepitaxial layer may comprise substantially the same electricalcharacteristics as the underlying single crystal semiconductor devicelayer 500. Alternatively, the epitaxial layer may comprise differentelectrical characteristics as the underlying single crystalsemiconductor device layer 500. An epitaxial layer may comprise amaterial selected from the group consisting of silicon, silicon carbide,silicon germanium, gallium arsenide, gallium nitride, indium phosphide,indium gallium arsenide, germanium, and combinations thereof. Dependingupon the desired properties of the final integrated circuit device, theepitaxial layer may comprise a dopant selected from among boron (ptype), gallium (p type), aluminum (p type), indium (p type), phosphorus(n type), antimony (n type), and arsenic (n type). The resistivity ofthe epitaxial layer may range from 1 to 50 Ohm-cm, typically, from 5 to25 Ohm-cm. In some embodiments, the epitaxial layer may have a thicknessbetween about 10 nanometers and about 20 micrometers, between about 20nanometers and about 3 micrometers, such as between about 20 nanometersand about 2 micrometers, such as between about 20 nanometers and about1.5 micrometers or between about 1.5 micrometers and about 3micrometers.

The finished SOI wafer comprises the single crystal semiconductor handlesubstrate 100, the epitaxial layer 200, the polycrystalline siliconcharge trapping layer 300, the dielectric layer 410 (e.g., buried oxidelayer), and the semiconductor device layer 500, may then be subjected toend of line metrology inspections and cleaned a final time using typicalSC1-SC2 process.

Example 1

Two groups of 200 mm diameter boron doped silicon (100) substrates withresistivity of 1,500 and 4,000 Ohm-cm, respectively, were used todemonstrate the advantage of using an engineered epitaxial layer toboost the RF performance. The substrates were cleaned using SC1/SC2clean in a commercial wet bench followed by epitaxial growth of asilicon layer of between 5 micrometers and 10 micrometers (5 micrometersin this example). Silicon epitaxial growth was conducted in a 200 mmCentura reactor at a temperature between 1000° C. and 1100° C. (1100° C.in this example) at atmospheric pressure. Trichlorosilane (TCS) was usedas the Silicon precursor, and H₂ as the carrier gas. Typical processconditions used to provide a growth rate of between 2 micrometers/minuteand 4 micrometers/minute (4 um/min in this example) growth rate were:TCS at a flow rate of 10 g/min, H₂ at a flow rate of 20 slm. Theepitaxial layer target resistivity was controlled between 200-2000Ohm-cm (1000 Ohm-cm in this example) by the growth temperature andn-type TCS background doping. After the silicon epitaxial layer wascomplete, the wafers were unloaded from the reactor and cleaned withSC1/SC2 to form a chemical oxide, which was followed by subsequent 2.8um thick polycrystalline silicon deposition in the same reactor usingthe same gas flows except that the deposition temperature is between900° C. and 1000° C. (950° C. in this example). The control wafer didnot receive silicon epitaxial growth but polycrystalline silicondeposition only. The wafers were then polished to form a smoothpolycrystalline silicon surface with only 2 um polycrystalline siliconleft and were used as the handle substrates for SOI manufacturing. BothSRP and Coplanar waveguide (CPW) RF measurements were conducted on thefinished SOI wafers. The SRP profile in FIG. 4 shows the substantiallyincreased resistivity from the polycrystalline silicon to the handlesubstrate in the engineered handle substrate because of the depletion ofthe epitaxial layer by the p-type handle substrate. As a result of thesignificantly reduced free carriers in the substrate, HD2 is reduced by10-15%. See FIG. 5. In order to achieve similar performance enhancementwithout the above disclosed engineering approach, a substrate withresistivity of 10 times higher is required, which is susceptible to typeflipping during the device fabrication thermal processes. Type flippingleads to uncontrollable substrate resistivity and poses negative impacton device performance.

Having described the invention in detail, it will be apparent thatmodifications and variations are possible without departing from thescope of the invention defined in the appended claims.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above products and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A method of preparing a multilayer substrate, themethod comprising: epitaxially depositing an epitaxial layer directly onthe front surface of a single crystal semiconductor handle substrate,wherein the single crystal semiconductor handle substrate comprises twomajor, generally parallel surfaces, one of which is the front surface ofthe single crystal semiconductor handle substrate and the other of whichis a back surface of the single crystal semiconductor handle substrate,a circumferential edge joining the front surface and the back surface ofthe single crystal semiconductor handle substrate, a central planebetween the front surface and the back surface of the single crystalsemiconductor handle substrate, and a bulk region between the front andback surfaces of the single crystal semiconductor handle substrate,wherein the single crystal semiconductor handle substrate has a minimumbulk region resistivity of at least about 500 ohm-cm and further whereinthe single crystal semiconductor handle substrate has a handle crystalorientation and wherein the epitaxial layer has a resistivity betweenabout 100 ohm-cm and about 5000 ohm-cm and further wherein the epitaxiallayer has a crystal orientation that is the same as the handle crystalorientation: depositing a charge trapping layer directly on theepitaxial layer, the charge trapping layer comprising polycrystallinesilicon having a resistivity of at least about 3000 ohm-cm; and bondinga dielectric layer directly on a front surface of a single crystalsemiconductor donor substrate to the charge trapping layer to therebyform a bonded structure, wherein the single crystal semiconductor donorsubstrate comprises two major, generally parallel surfaces, one of whichis the front surface of the semiconductor donor substrate and the otherof which is a back surface of the semiconductor donor substrate, acircumferential edge joining the front and back surfaces of thesemiconductor donor substrate, and a central plane between the front andback surfaces of the semiconductor donor substrate, wherein the singlecrystal semiconductor donor substrate comprises a cleave plane.
 2. Themethod of claim 1 wherein the single crystal semiconductor handlesubstrate comprises single crystal silicon.
 3. The method of claim 1wherein the single crystal semiconductor donor substrate comprisessingle crystal silicon.
 4. The method of claim 1 wherein the singlecrystal semiconductor handle substrate has a bulk resistivity betweenabout 1000 Ohm-cm and about 100,000 Ohm-cm.
 5. The method of claim 1wherein the single crystal semiconductor handle substrate has a bulkresistivity between about 1000 Ohm-cm and about 6,000 Ohm-cm.
 6. Themethod of claim 1 wherein the single crystal semiconductor handlesubstrate comprises an electrically active dopant selected from thegroup consisting of boron, aluminum, gallium, indium, and anycombination thereof.
 7. The method of claim 1 wherein the epitaxiallayer has a resistivity between about 200 ohm-cm and about 2000 ohm-cm.8. The method of claim 1 wherein the epitaxial layer has a resistivitybetween about 400 ohm-cm and about 1000 ohm-cm.
 9. The method of claim 1wherein the epitaxial layer comprises silicon and an electrically activedopant selected from the group consisting of arsenic, phosphorus,antimony, and any combination thereof.
 10. The method of claim 9 whereinthe epitaxial layer comprising silicon is between about 0.2 micrometersand about 20 micrometers thick.
 11. The method of claim 9 wherein theepitaxial layer comprising silicon is between about 0.5 micrometers andabout 10 micrometers thick.
 12. The method of claim 1 wherein theepitaxial layer comprises silicon doped with carbon at a carbonconcentration between about 0.1 mole % and about 5 mole %.
 13. Themethod of claim 12 wherein the epitaxial layer comprises silicon dopedwith carbon at a carbon concentration between about 0.5 mole % and about2 mole %.
 14. The method of claim 12 wherein the epitaxial layercomprising silicon doped with carbon is between about 0.1 micrometersand about 10 micrometers thick.
 15. The method of claim 1 wherein thecharge trapping layer has a resistivity of at least about 7000 ohm-cm.16. The method of claim 1 further comprising forming an insulating layeron the charge trapping layer prior to bonding with the dielectric layeron the front surface of the single crystal semiconductor donorsubstrate, wherein the insulating layer comprises semiconductor oxide orsemiconductor oxynitride.
 17. The method of claim 1 wherein thedielectric layer comprises a material selected from the group consistingof silicon dioxide, silicon nitride, silicon oxynitride, hafnium oxide,titanium oxide, zirconium oxide, lanthanum oxide, barium oxide, and acombination thereof.
 18. The method of claim 1 further comprisingheating the bonded structure at a temperature and for a durationsufficient to strengthen the bond between the dielectric layer of thesingle crystal semiconductor donor substrate and the charge trappinglayer on the front surface of the single crystal semiconductor handlesubstrate.
 19. The method of claim 1 further comprising mechanicallycleaving the bonded structure at the cleave plane of the single crystalsemiconductor donor substrate to thereby prepare a cleaved structurecomprising the single crystal semiconductor handle substrate, theepitaxial layer, the charge trapping layer, the dielectric layer, and asingle crystal semiconductor device layer.
 20. A method of preparing amultilayer substrate, the method comprising: epitaxially depositing anepitaxial layer directly on the front surface of a single crystalsemiconductor handle substrate, wherein the comprises single crystalsemiconductor handle substrate two major, generally parallel surfaces,one of which is the front surface of the single crystal semiconductorhandle substrate and the other of which is a back surface of the singlecrystal semiconductor handle substrate, a circumferential edge joiningthe front surface and the back surface of the single crystalsemiconductor handle substrate, a central plane between the frontsurface and the back surface of the single crystal semiconductor handlesubstrate, and a bulk region between the front and back surfaces of thesingle crystal semiconductor handle substrate, wherein the singlecrystal semiconductor handle substrate comprises an electrically activep-type dopant selected from the group consisting of boron, aluminum,gallium, indium, and any combination thereof and further wherein thesingle crystal semiconductor handle substrate has a handle crystalorientation and wherein the epitaxial layer comprises an electricallyactive n-type dopant selected from the group consisting of arsenic,phosphorus, antimony, and any combination thereof, wherein theconcentration of the electrically active n-type dopant is less thanabout 1×10¹⁴ atoms/cm³ and further wherein the epitaxial layer has acrystal orientation that is the same as the handle crystal orientation:depositing a charge trapping layer directly on the epitaxial layer, thecharge trapping layer comprising polycrystalline silicon; and bonding adielectric layer directly on a front surface of a single crystalsemiconductor donor substrate to the charge trapping layer to therebyform a bonded structure, wherein the single crystal semiconductor donorsubstrate comprises two major, generally parallel surfaces, one of whichis the front surface of the semiconductor donor substrate and the otherof which is a back surface of the semiconductor donor substrate, acircumferential edge joining the front and back surfaces of thesemiconductor donor substrate, and a central plane between the front andback surfaces of the semiconductor donor substrate, wherein the singlecrystal semiconductor donor substrate comprises a cleave plane.
 21. Themethod of claim 20 wherein the single crystal semiconductor handlesubstrate comprises single crystal silicon.
 22. The method of claim 20wherein the single crystal semiconductor donor substrate comprisessingle crystal silicon.
 23. The method of claim 20 wherein the singlecrystal semiconductor handle substrate comprises the electrically activep-type dopant at a concentration of less than about 2×10¹³ atoms/cm³.24. The method of claim 20 wherein the single crystal semiconductorhandle substrate comprises the electrically active p-type dopant at aconcentration of less than about 1×10¹³ atoms/cm³.
 25. The method ofclaim 20 wherein the single crystal semiconductor handle substratecomprises the electrically active p-type dopant at a concentration ofless than about 5×10¹² atoms/cm³.
 26. The method of claim 20 wherein theconcentration of the electrically active n-type dopant in the epitaxiallayer is less than about 1×10¹³ atoms/cm³.
 27. The method of claim 20wherein the concentration of the electrically active n-type dopant inthe epitaxial layer is less than about 5×10¹² atoms/cm³.
 28. The methodof claim 20 wherein the epitaxial layer comprises silicon.
 29. Themethod of claim 28 wherein the epitaxial layer comprising silicon isbetween about 0.2 micrometers and about 20 micrometers thick.
 30. Themethod of claim 20 wherein the epitaxial layer comprises silicon dopedwith carbon at a carbon concentration between about 0.1 mole % and about5 mole %.
 31. The method of claim 20 wherein the epitaxial layercomprises silicon doped with carbon at a carbon concentration betweenabout 0.5 mole % and about 2 mole %.
 32. The method of claim 20 whereinthe charge trapping layer has a resistivity of at least about 3000ohm-cm.
 33. The method of claim 20 wherein the charge trapping layer hasa resistivity of at least about 7000 ohm-cm.
 34. The method of claim 20further comprising forming an insulating layer on the charge trappinglayer prior to bonding with the dielectric layer on the front surface ofthe single crystal semiconductor donor substrate, wherein the insulatinglayer comprises semiconductor oxide or semiconductor oxynitride.
 35. Themethod of claim 20 wherein the dielectric layer comprises a materialselected from the group consisting of silicon dioxide, silicon nitride,silicon oxynitride, hafnium oxide, titanium oxide, zirconium oxide,lanthanum oxide, barium oxide, and a combination thereof.
 36. The methodof claim 20 further comprising heating the bonded structure at atemperature and for a duration sufficient to strengthen the bond betweenthe dielectric layer of the single crystal semiconductor donor substrateand the charge trapping layer on the front surface of the single crystalsemiconductor handle substrate.
 37. The method of claim 20 furthercomprising mechanically cleaving the bonded structure at the cleaveplane of the single crystal semiconductor donor substrate to therebyprepare a cleaved structure comprising the single crystal semiconductorhandle substrate, the epitaxial layer, the charge trapping layer, thedielectric layer, and a single crystal semiconductor device layer.